Among hydraulic composition admixtures, there are those called high-performance water-reducing agents having a high effect of conferring fluidity. Typical examples thereof include a naphthalenesulfonic acid/formaldehyde condensate salt (based on naphthalene), a melaminesulfonic acid/formaldehyde condensate salt (based on melamine), and a polycarboxylic acid having a polyoxyalkylene chain. However, when highly water-reduced concrete is prepared by using a cement dispersant, slump loss is significant and there is a problem of deterioration in workability with respect to filling property and applicability.
Accordingly, it has been proposed that a water-soluble vinyl copolymer having slump loss preventing performance by itself is used as a cement dispersant.
Concrete prepared by using, as hydraulic powder, high belite cement (cement with a high content of C2S as a cement component) such as moderate heat Portland cement or low heat Portland cement or a slag cement compounded with blast-furnace slag cement may decrease slump flow over time because of a reduced amount of a cement dispersant added to attain required fluidity.
High strength concrete has a problem such as high concrete viscosity because this concrete is prepared by kneading at a lower water/hydraulic powder ratio (hereinafter referred to as water/cement ratio) than in normal strength (general strength) concrete.
This problem of increase in viscosity is still not sufficiently solved even by the polycarboxylic acid-based water reducing agent, so there has been demand for an additive having a higher effect of reducing concrete viscosity.
Under this background, JP-A 11-157897 discloses an admixture excellent in an ability to reduce the viscosity of high-strength concrete and to suppress delay in concrete setting, which contains as an essential component a vinyl copolymer containing a long-chain oxyalkylene group, a short-chain oxyalkylene group and a specific monomer.
JP-A 2000-327386 proposes that a polymer having both a monoester or monoether having a polyalkylene glycol chain and a monomer having an unsaturated bond and a phosphate group is used to obtain a cement dispersant capable of exhibiting excellent flow characteristics, a high dispersing effect and rapid setting, regardless of the water compounding ratio in concrete.
WO-A 2006/006732 distributed on Jan. 17, 2006 discloses a polymer obtained from 3 kinds of monomers and use thereof in a hydraulic composition.